LeBron James' postseason performance so far has been absolutely mesmerizing.

From his 45-point performance against the Boston Celtics in Game 6 of the 2012 Eastern Conference Finals with his legacy on the line, to his 40-point explosion against the Indiana Pacers when everyone was doubting his will, LeBron has had one of the most memorable postseasons in recent memory.

Those remarkable performances won't mean anything though if LeBron fails once again to obtain the first NBA title of his career.

Ahead are five reasons why LeBron's amazing performance in the 2012 Eastern Conference finals won't mean anything if he fails to win the 2012 NBA title.

This All Happened Last Year ...

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Last year at the end of the Eastern Conference finals, when the Miami Heat knocked off the Chicago Bulls, everyone was talking about how LeBron had stepped up his game and was ready to take his legacy to the next level.

After averaging 25.8 points, 7.8 rebounds and 6.6 assists per game against the Bulls, we were all ready to declare that LeBron had finally become the player we all knew he could be.

That all changed once he failed to lead the Heat against the Dallas Mavericks, with just 17.8 points per game in the 2011 NBA Finals.

Fast forward an entire year, and we're back to the exact same place. LeBron has once again elevated his game and carried the Heat to their second straight NBA Finals appearance. This time, he's done so in more captivating fashion—averaging 33.6 points, 11 rebounds and 3.9 assists in this year's Eastern Conference finals.

I'm not saying that LeBron won't carry the Heat to the 2012 NBA title, but I'm just reminded you that we saw the exact same thing from LeBron and Co. last year around this time. Which is reason enough to be hesitant when it comes to proclaiming that LeBron has finally become the player he needs to be.

The point is that LeBron's had other incredible playoff performances in his career, and they aren't as well-remembered because in all of those seasons he failed to attain the ultimate goal of winning an NBA title.

If the same happens this season, his 45-point performance in Game 6, and his 32-point explosion in Game 7 will fall into the same category of being tainted by failing to hoist the Larry O'Brien trophy.

The Boston Celtics Aren't Exactly the Oklahoma City Thunder

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No disrespect to the Boston Celtics, but no one thought the Celtics would give the Heat the kind of series they did. The Celtics are one of the oldest teams in the NBA, with the combined age of their big three around 86 years.

Kevin Garnett, Ray Allen and Paul Pierce are certainly one of the greatest trios in NBA history, but beating them, like the Heat did last year, won't be considered as impressive as knocking out the "new trio" in the NBA—consisting of Kevin Durant, James Harden and Russell Westbrook.

If LeBron is able to carry the Heat past the upstart Thunder in the NBA Finals, his epic 2011-12 season will be capped off by proving that he can lead the Heat against the veteran teams in the NBA like the Boston Celtics, while also being able to knock off the young, athletic teams in the NBA like the Thunder.

Against the Thunder this season, LeBron averaged 25.5 points, five rebounds and 8.6 assists per game. LeBron will have to increase his production, like he's done all postseason long, if he wants to lead the Heat over the Thunder.

Doing that will not only earn LeBron his first NBA title, it will also make a bold statement to the rest of the NBA that he's ready to pull through on his "not one ... not two ... not three ... " promise.

A career-defining performance against the young and athletic Thunder will mean more for LeBron's career than his classic performance against the Celtics. Failing to beat the Thunder will result in fans forgetting about everything that happened before the NBA Finals, just like they did last season.

LeBron's 2012 NBA Finals Performance Means More for Legacy Than Playoffs so Far

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LeBron James knows better than any other NBA player that legacies are defined by the amount of NBA titles won, not the amount of memorable playoff performances.

I've already gone over the insane amount of epic playoff performances that LeBron's produced over the span of his nine-year NBA career. Those memorable moments won't mean anything, though, if LeBron fails for a second straight year to enter the realm of NBA champion.

While I hate to say it, the way that LeBron plays in the 2012 NBA Finals will have more bearing on his legacy than the way he's played throughout the postseason so far.

Let's run through some hypothetical NBA Finals scenarios for LeBron, and how it will impact his legacy.

If the Heat beat the Thunder, but LeBron averages 2011 NBA Finals' numbers, around 17.8 points per game, his lack of production in the finals will be remembered more than anything he did in the 2012 postseason.

If the Heat lose to the Thunder and LeBron averages around his current postseason averages of 30 points, 10 rebounds and five assists, everyone will question his ability to ever win an NBA title, and how he just doesn't have that "elite mindset."

Finally, if the Heat beat the Thunder and LeBron averages around his current postseason averages, he'll finally become the player that everyone wants him to be, and while that might not matter to him, it will matter for his legacy.

This Year Is 'Championship or Bust' for LeBron and the Heat

If you've turned on ESPN or graced the pages of Bleacher Report at least once within the last eight months, you've heard about this year being "championship or bust" for the Miami Heat.

There's no doubt that it's the truth.

An Eastern Conference title means nothing for LeBron and Co. in the scheme of things this year, and it ultimately means nothing for LeBron's legacy. In all honesty, the more Eastern Conference titles LeBron wins, without winning an NBA title, will do more damage to LeBron's legacy than it helps.

More than any season in LeBron's nine-year NBA career, this season means the most. LeBron finally has had enough time to gel together with his teammates in South Beach and he's already failed once at achieving his lifetime goal of being an NBA champion with the Heat.

Failing this season, after such a prolific outing in the playoffs so far, will hurt LeBron's legacy much more than any other season has.

It's time for LeBron to finally become an NBA champion, and if his historic 2011-12 season comes to an end without hoisting the 2012 Larry O'Brien Championship trophy his legacy will in most respects be tarnished beyond repair.

Without the 2012 NBA title, LeBron's magical and memorable playoff run will mean absolutely nothing, since it's "championship or bust" for LeBron and the Heat.